embedded 3d bioprinting of esophageal muscle-layer analogs for tissue engineering

Advancing 3D Bioprinting with &#954;-Carrageenan Sub-Microgel Medium

Tissue engineering scaffolds, including electro-spun fibers, porous sponges, and polymer hydrogels, play a pivotal role in the repair and reconstruction of damaged tissues and organs by providing a structural framework supporting cell growth, tissue regeneration, and the restoration of organ function1,2,3. However, traditional scaffolds encounter challenges in accurately replicating native tissue structures, leading to a mismatch between the engineered and natural tissues. This limitation hinders the efficient healing of defective tissues, emphasizing the urgent need for scaffold design advancements to achieve more accurate biomimicry. Three-dimensional (3D) bioprinting is an innovative manufacturing technique that precisely constructs complex biological tissue structures layer by layer using biomaterial inks and cells4. Among various biomaterials, polymer hydrogels emerge as ideal bioinks with their distinctive network that facilitates in situ encapsulation of cells and crucially supports their growth5,6. Nevertheless, many soft and highly hydrated hydrogels tend to induce blurring or rapid collapse of printed scaffold structures during the printing process when used as bioinks. To address this challenge, embedded 3D bioprinting technology employs a microgel bath as a support material, allowing precise soft bioink deposition. Upon gelation of the hydrogel bioinks, refined bionic scaffolds with intricate structures are obtained by removing the microgel bath. Materials like gelatin7,8, agarose9, and gellan gum10,11 have been employed to create microgel baths for embedded 3D bioprinting, significantly advancing the application of soft hydrogels in tissue engineering. However, the micron-level and non-uniform particle size of these particulate gels detrimentally impacts the resolution and fidelity of 3D printing12,13,14. There is an urgent need to fabricate a gel-like suspension float with small and uniformly dispersed particles, offering advantages in achieving high-fidelity bioprinting.
In this protocol, a novel sacrificial granulate &#954;-carrageenan suspension bath with a uniform sub-micron level is presented for embedded 3D printing. This innovative sub-microgel bath behavior of rapid jamming-unjamming transition facilitates the precise fabrication of biomimetic hydrogel scaffolds with high structural fidelity15. Utilizing this new suspension medium, a series of biomimetic tissue and organ constructs featuring multi-layer tissue structures are successfully printed, employing a composite bioink composed of gelatin methacrylate and silk fibro methacrylate. In this study, we chose the esophagus as the 3D bioprinting biomimetic object mainly because the esophagus not only has a multi-layered tissue structure but also its muscle layer exhibits an internal circular and external longitudinal complex layering structure. Ensuring proper alignment and organization of these layers is essential for functional tissue regeneration. Therefore, we highly desire to replicate the multilayered architecture of the esophagus. More importantly, we utilized &#954;-carrageenan sub-microgels as the suspension bath and GelMA/SFMA as the bioink to design and construct a biomimetic scaffold for tissue engineering. The printed esophagus can be easily released by repeated phosphate-buffered saline washing. Moreover, the &#954;-carrageenan sub-microgel bath is free of cytotoxic substances, ensuring high cytocompatibility15. The smooth muscle cells loaded within anisotropic scaffolds exhibit a notable spreading activity. This uniform sub-microgel suspension medium offers a new avenue for the fabrication of complex tissues and organs through embedded 3D bioprinting.

Author Spotlight: Development of Homogeneous &#954;-Carrageenan Sub-Microgel Baths for High-Resolution 3D Bioprinting

Embedded Bioprinting of Tissue-like Structures Using &#954;-Carrageenan Sub-Microgel Medium

3D bioprinting in a microgel-based suspension bath has provided a versatile platform for fabricating complex 3D structures using soft hydrogels, but it is still limited by the low print resolution and accuracy, hindering the practical applications of the printed products in tissue engineering. The present microgel baths often exhibit large sizes and poor dispersions, resulting in a big diameter and irregular morphology of the printed filaments. Therefore, it poses a significant challenge in preparing a microgel bath with a small particle size and uniform morphology.This protocol offers the fabrication of a homogenous and biocompatible cationic cross-linked kappa-carrageenan sub-microgel bath for high-fidelity bioprinting, through an easy-to-operate mechanical grinding strategy, Since kappa-carrageenan sub-microgels exhibit a uniform methodology with a small particle size of 565 nanometer, and a low state of 0.35%enabling precise tissue and organ construction with remarkable fidelity and high resolution.

Embedded 3D Bioprinting of Esophageal Muscle-Layer Analogs for Tissue Engineering

To begin, take the cultured esophageal smooth muscle cells once they attain 80%co fluency. Aspirate the medium and wash the endothelial smooth muscle cells with five milliliters of PBS. Then add two milliliters of 0.2%Trypsin-EDTA to the flask and incubate for two minutes to digest the cells.Add two milliliters of DMEM to terminate the digestion process and transfer the cell suspension to a 15 milliliter centrifuge tube. Centrifuge the tube at 675G for three minutes. Carefully aspirate the supernatant, and resuspend the cell pellet in the composite gelatin methacrylate and silk fibroin methacryloyl bioinks.After bioprinting and washing the 3D esophageal muscle layer with PBS, carefully aspirate the PBS and replace it with three milliliters of DMEM, supplemented with 10%FBS, and 1%penicillin or streptomycin.

Research

JoVE Journal

Engineering

Embedded three-dimensional (3D) bioprinting utilizing a granular hydrogel supporting bath has emerged as a critical technique for creating biomimetic ...